Single shaft type table feed device

ABSTRACT

A single shaft type table feed device comprises a movable body and an auxiliary movable body  34.  The movable body is supported by a guide rail  31  and can be freely moved by a feed screw shaft  35  in the axial direction thereof. The auxiliary movable body  34  includes an inside diameter portion through which the feed screw shaft  35  can be inserted. The auxiliary movable body  34  is supported by the guide rail  31  and freely movable in the axial direction thereof. The inside diameter portion  38   a  of the auxiliary movable body  34  is slidingly contacted with the feed screw shaft  35.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a single shaft type table feeddevice including a movable body and an auxiliary movable body and, inparticular, to a single shaft type table feed device in which theauxiliary movable body can fill a role of the part of an intermediatesupport, to thereby be able to enhance the critical speed of a feedscrew shaft.

[0002] Conventionally, as a table feed device using a feed screw shaft,there are known various types of table feed devices. One of them is asingle shaft type table feed device which is a feed screw integrallycombined linear guide device obtained by combining a feed screw devicewith a linear guide device into an integrally united body.

[0003] In particular, a single shaft type table feed device to beimproved by the invention is a single shaft type table feed device inwhich there are mounted not only a movable body including a screw nutportion engageable with the feed screw shaft but also an auxiliarymovable body not including a screw nut portion so as to enhance theresistance of the feed screw shaft to a load applied thereto.

[0004] Recently, there has been increasing a demand for enhancing thefeed speed of the single shaft type table feed device of this kind.

[0005] By the way, in the table feed device using a feed screw shaft, ifthe number of working rotations of the feed screw shaft approaches thenatural frequency of the feed screw shaft, then it becomes a so calledcritical speed, thereby producing resonance. Since the critical speed isin inverse proportion to the square of the support distance of the feedscrew shaft, if the support distance is set as short as possible tothereby enhance the natural frequency of the feed screw shaft, then thecritical speed of the feed screw shaft -can be increased effectively.Therefore, in a feed screw shaft having a long length, generally, asshown in FIG. 7, an intermediate support 2 in sliding engagement withthe feed screw shaft 1 is set at an intermediate position in the supportdistance of the feed screw shaft on a base member. In this case, inorder to prevent interference between the intermediate support 2 and anut 4 which is in threadedly engagement with the feed screw shaft 1 andis mounted on a table 3, there is provided a limit switch 5; that is,when the table 3 passes, the intermediate support 2 can be retreated inaccordance with the limit switch 5.

[0006] Also, in the Japanese Patent No. 2526816, there is disclosedanother example of the intermediate support. In this intermediatesupport, as shown in FIG. 8, two guide rails 7 are fixed to two sideportions of a base member in parallel to each other, a pair of tablelinear motion bearings (that is, table sliders) 8 are fitted on each ofthe two guide rails 7 in such a manner that they can be freely moved inthe axial direction of the guide rails, and a table 3 is fixed to eachof the table sliders 8 on the top surfaces thereof. A feed screw shaft 1is interposed between and extended in parallel to the two guide rails;in particular, one end side of the feed screw shaft 1, which is to beconnected with a drive motor 13, is supported by a support unit 11,whereas the opposite end side thereof is supported by a support bearing12. An intermediate support 14 is interposed between the support bearing12 and a table nut 4 which is threadedly engaged with the feed screwshaft 1 through balls. Also, the intermediate support 14 includes anintermediate support frame 16 which is supported by intermediate supportlinear motion bearings (that is, intermediate support sliders) 15, 15respectively fitted with the guide rails 7, 7, and an intermediatesupport nut 17 which is threadedly engaged with the feed screw shaft 1through balls and is supported in such a manner that it is preventedfrom moving in the axial direction with respect to the intermediatesupport frame 16 but can be rotated freely. On the other hand, betweenthe feed screw shaft 1 and one-guide rail 7, there is disposed anauxiliary feed screw device 20 which comprises an auxiliary feed screw18 having an axis parallel to the feed screw shaft 1 and supported onthe base member, and an intermediate support feed nut 19 which isthreadedly engaged with the present auxiliary feed screw 18. And, theintermediate support feed nut 19 is fixed to and mounted on theintermediate support frame 16 of the intermediate support 14. Also, theend portion of the auxiliary feed screw 18 having a uniform pitch andthe end portion of the feed screw shafts I are connected together byauxiliary feed screw drive means 21 which comprise a timing belt and atiming pulley in such a manner that the auxiliary feed screw 18 can berotated at one half of the number of rotations of the feed screw shaft1. With use of the intermediate support 14, if the feed screw shaft 1 isdriven or rotated by the drive motor 13, then the table nut 4 is movedand, in linking with the movement of the table nut 4, the intermediatesupport 14 is moved in the same direction by an amount of one half ofthe moving amount of the table nut 4. Due to this, the intermediatesupport 14 is always allowed to support the feed screw shaft 1 almostcentrally between the table nut 4 and support bearing 12, thereby beingable to enhance the critical speed of the feed screw shaft 1.

[0007] Conventionally, a single shaft type table feed device includingan auxiliary movable body increases a span between the nut portion ofthe movable body and the supporting shaft, because the auxiliary movablebody having an unloaded hole which is not engaged with the feed screwshaft is interposed between a movable body including a nut portion to bethreadedly engaged with a feed screw shaft and a bearing for supportingthe end portion of the feed screw shaft.

[0008] As a result, the natural frequency of the feed screw shaft islowered, that is, the critical speed is lowered, thereby often raising aproblem that the use of the single shaft type table feed device at thehigh speed feed is limited. As a measure to deal with this problem,there can be provided an intermediate support in the single shaft typetable feed device.

[0009] However, in the conventional intermediate support 2 shown in FIG.7, there is found a drawback as follows: that is, it is necessary toprovide a retreat mechanism which is capable of retreating theintermediate support 2 when the table 3 or table nut 4 passes throughthe intermediate support 2. In fact, the retreat mechanism iscomplicated in structure and, therefore, it is not proper fromviewpoints of not only cost but also space to use the conventionalintermediate support 2 including such complicated retreat mechanism asan intermediate support of a single shaft type table feed deviceinherently having a compact structure.

[0010] On the other hand, in the conventional intermediate support 14shown in FIG. 8 as well, there is also found a drawback as follows: thatis, it is necessary to provide the auxiliary feed screw device 20 whichis capable of moving the intermediate support 14 in linking with thetable nut 4, but the auxiliary feed screw device 20 is complicated instructure. Therefore, similarly to the intermediate support 2, it is notproper to use the conventional intermediate support 14 as anintermediate support of a compact single shaft type table feed devicefrom viewpoints of cost and space.

SUMMARY OF THE INVENTION

[0011] In view of the above circumstances of the prior art, the presentinventors have studied how to increase the speed of the single shafttable feed device which includes the movable body and auxiliarymovable-body and is easy to incur the lowered critical speed, and havefinally found a unique fact that if the auxiliary movable bodyconventionally formed in such a manner as not to be engaged with thefeed screw shaft can fill the role as an intermediate support, then thecritical speed of the feed screw shaft can be increased.

[0012] Accordingly, it is an object of the invention to provide a singleshaft type table feed device which is capable of increasing the criticalspeed of the feed screw shaft and thus realizing a high speed feedoperation at a low cost and in a compact structure.

[0013] In attaining the above object, according to the invention, thereis provided a single shaft type table feed device which comprises:

[0014] a single feed screw shaft extending in an axial direction;

[0015] a guide rail extending in parallel with the screw shaft;

[0016] a movable body movably supported by the guide rail and fed by thescrew shaft in the axial direction; and

[0017] an auxiliary movable body disposed apart from the movable body inthe axial direction for supporting the table, the auxiliary movable bodymovably supported by the guide rail in the axial direction and moved inlinking with a movement of a table mounted on the movable body.

[0018] In the above-mentioned single shaft type table feed device, it ispreferable that the auxiliary movable body includes an inside diameterportion through which the feed screw shaft can be inserted, and theinside diameter portion of the auxiliary movable body is contactablewith the said feed screw shaft.

[0019] In the above-mentioned single shaft type table feed device, it ispreferable that the inside diameter portion of the auxiliary movablebody is disengaged with said feed screw shaft in a normal operation, butis contacted with the same when the feed screw shaft is vibrated.

[0020] In the above-mentioned single shaft type table feed device, it isadvantageous that the inside diameter portion of the auxiliary movablebody is slidably contacted with the feed screw shaft.

[0021] Here, to bring the auxiliary movable body into sliding contactwith the feed screw shaft, a sliding contact member to be ligthlycontactable with the feed screw shaft may be inserted into the insidediameter portion of the auxiliary movable body.

[0022] The sliding contact member may be preferably formed in acylindrical shape. In addition to this, it is preferable that in orderto facilitate the mounting of the sliding contact member, thecylindrical shape of the sliding contact member may also be divided inthe peripheral direction thereof and then may be fastened by an elasticbody, such as garter spring or the like.

[0023] Further, the cylindrical shape of the sliding contact member mayalso be divided in the axial direction thereof and may be then mountedonto the inside diameter portion of the auxiliary movable body.

[0024] Furthermore, the sliding contact member may comprise a lubricantcontaining member.

[0025] Moreover, the auxiliary movable body may be brought in threadedlyengagement with the feed screw shaft.

[0026] Furthermore, the sliding contact member may be mounted spirallyon the inside diameter portion of the auxiliary movable body. In thiscase, the spirally winding direction of the sliding contact member maybe matched to the screw shape of the screw groove of the feed screwshaft and thus the sliding contact member may be threadedly engaged withthe feed screw shaft.

[0027] Moreover, a sliding contact member with a screw may be structuredsuch that it can be rotated on the auxiliary movable body. In this case,since the auxiliary movable body can be fixed at an arbitrary positionin the axial direction of the feed screw shaft, the support distancenecessary for an intermediate support can be decided arbitrarily andthus the critical speed of the feed screw shaft can be adjustedproperly.

[0028] As material suitable for the sliding contact member, there ran beused fluorine resin having a good sliding property; a crystallinepolymer such as nylon, POM, PST, PET, PPS, PEEK, or the like; a polymeralloy (a multi-component system containing two or more kinds ofpolymers); a composite plastics containing reinforcing fibers or thelike; and, other similar material. Also, it is also possible to usematerial having a lubricating property, for example, lubricantcontaining resin, a solid lubricant such as molybdenum sulfide or thelike. In this case, not only the critical speed of the feed screw shaftcan be enhanced but also the lubrication of the feed screw can becarried out.

[0029] Further, as means for fixing the sliding contact member to theinside diameter portion of the auxiliary movable body, there can be useda fixing screw which is capable of fastening the auxiliary movable bodyfrom outside. Also, as in an embodiment to be discussed later herein, itis also possible to use end caps which are respectively mounted on thetwo end portions of the auxiliary movable body in the axial directionthereof.

[0030] Note that, in the present invention, the term “the insidediameter portion of an auxiliary movable body” on which the slidingcontact member is to be mounted means not only the inside diameterportion of the main body of the auxiliary movable body (for example, asub-slider main body) but also the inside diameter portion of anattachment to be mounted on the main body of the auxiliary movable body(for example, the inside diameter portions of the end caps to be mountedon the two end portions of the sub-slider main body). Therefore, theinvention also implies that the sliding contact member is mounted on theinside diameter portion of an attachment of an auxiliary movable body tothereby bring the sliding contact member into sliding contact with thefeed screw shaft.

[0031] Also, according to the invention, even if the inside diameterportion of the auxiliary movable body is not slidingly contacted withthe feed screw shaft, by setting a clearance between the inside diameterportion of the auxiliary movable body and the outside diameter surfaceof the feed screw shaft in such a manner as to have a size which allowsthe former to be contacted with the latter when the latter, namely, thefeed screw shaft is vibrated, the auxiliary movable body can fill therole as an intermediate support.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a plan view of the whole of a first embodiment of asingle shaft type table feed device according to the invention;

[0033]FIG. 2 is a side view of the whole of the first embodiment;

[0034]FIG. 3 is a partially cutaway perspective view of the firstembodiment, showing the structure of an auxiliary movable body employedin the first embodiment;

[0035]FIG. 4 is a partially cutaway perspective view of the firstembodiment, showing the structure of a movable body employed in thefirst embodiment;

[0036]FIG. 5 is a partially cutaway perspective view of a secondembodiment of a single shaft type table feed device according to theinvention, showing the structure of an auxiliary movable body employedin the second embodiment;

[0037]FIG. 6 is a partially cutaway perspective view of a thirdembodiment of a single shaft type table feed device according to theinvention, showing the structure of an auxiliary movable body employedin the third embodiment;

[0038]FIG. 7 is a schematic view of an example of a conventionalintermediate support; and

[0039]FIG. 8 is a schematic view of another example of a conventionalintermediate support.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Now, description will be given below of the preferred embodimentsof a single shaft type table feed device according to the invention withreference to the accompanying drawings.

[0041] Embodiment 1

[0042] Firstly, description will be given below of a first embodiment ofa single shaft type table feed device according to the invention withreference to FIGS. 1 to 4.

[0043] Now, FIGS. 1 to 4 respectively show the structure of a firstembodiment of a single shaft type table feed device according to theinvention. In particular, FIG. 1 is a plan view of the whole of thesingle shaft type table feed device. FIG. 2 is a side view thereof. FIG.3 is a perspective view of thereof, in which the structure of anauxiliary movable body employed in the single shaft type table feeddevice is shown in a partially cutaway manner. FIG. 4 is a perspectiveview of thereof, in which the structure of a movable body employed inthe single shaft type table feed device is shown in a partially cutawaymanner.

[0044] As can be seen clearly from these figures, the present singleshaft type table feed device comprises a guide rail 31, a slider 33, asub-slider 34 and a ball shaft 35. The guide rail 31 has a substantiallyU-shaped cross section, includes two ball rolling grooves 31 arespectively formed in the two opposed inner surfaces thereof, and isextended in the axial direction thereof. The slider 33 serves as amovable body which is fitted with the guide rail 31 in such a manner asto be freely movable in the axial direction thereof. The sub-slider 34serves as an auxiliary movable body. A ball shaft 35 serves as a feedscrew shaft which is extended along the axis of the guide rail 31 andthe two ends of which are supported rotatably through bearings (notshown).

[0045] One shaft end portion 35 a of the ball screw shaft 35 isprojected outwardly of the guide rail 31 and can be connected with theoutput shaft of a drive motor (not shown).

[0046] The slider 33 and sub-slider 34 respectively comprise main bodies33 a and 34 a, and end caps 33 b and 34 b are removably mounted on theirrespective two end portions of main bodies 33 a and 34 a, respectively.And, on the respective two side surfaces of the main bodies 33 a and 34a, there are respectively formed ball rolling grooves 33 c and 34 cwhich are respectively opposed to the ball rolling grooves 31 a of theguide rail 31. Between the ball rolling grooves 31 a of the guide rail31 and the ball rolling grooves 33 c and 34 c opposed to the ballrolling grooves 31 a, there are interposed a large number of linearmotion guiding balls 32. Also, in the end caps 33 b and 34 b on the twofront and rear end faces of the respective main bodies 33 a and 34 a,there are formed circulation passages which are used to cause the balls32 to make a U-turn so that the balls 32 can be made to circulate in anendless manner. Due to the rolling motion of the balls 32, the slider 33and sub-slider 34, while sharing the load given from a table (not shown)mounted on their respective upper surfaces by screws, can be movedsmoothly in the axial direction of the guide rail 31 under the guide ofthe guide rail 31.

[0047] The ball screw shaft 35 is inserted through the core of thesub-slider 34. Therefore, in the slider main body 34 a, there is formeda cylindrical-shaped screw shaft insertion hole 37 in a so called“unloaded hole” manner. Also, in each of the end caps 34 b and 34 bmounted on the two end portions of the sub-slider 34, there is formed ina unloaded hole manner a screw shaft insertion hole 36 slightly smallerin diameter than the screw shaft insertion hole 37. On the insidediameter surface of the insertion hole 37 of the sub-slider main body 34a, as shown in FIG, 3, there is mounted a cylindrical-shaped slidingcontact member 38, for example, by inserting the same with pressure, orby other similar means and the sliding contact member 38 is restrictedin the axial direction thereof by the end caps 34 b respectively mountedon the two end portions of the sub-slider 34, The sliding contact member38 is structured such that the inside diameter portion 38 a thereof isin sliding contact with the outer peripheral surface of the ball screwshaft 35. The reason for use of this sliding contact is to give thesub-slider 34, which is originally provided so as to enhance theresistance-to-load of the ball screw shaft, the function of anintermediate support for supporting the intermediate portion of the ballscrew shaft 35; that is, the sliding contact member 38 may have only thesize which is capable of supporting the ball screw shaft 35. Therefore,the sliding contact member 38 must not be always slidingly contactedwith the whole circumference of the ball screw shaft 35; but, forexample, it is also possible to employ a partial sliding contactstructure in which the cylindrical shape of the sliding contact member38 may be opened in part in the axial direction thereof and isthereafter mounted on the ball screw shaft 35, so that the slidingcontact member 38 is slidingly contacted with the circumference of theball screw shaft 35 in such a manner it is not slidingly contacted withsome part of the circumference of the ball screw shaft 35.

[0048] In the single shaft type table feed device according to theinvention, preferably, the sliding contact member 38 may be moved inlinking with the movement of the table while in sliding contact with theball screw shaft 35. For this reason, the sliding contact member 38 isformed of material having a good sliding motion property such asfluorine resin or the like. However, as the material of the slidingcontact member 38, besides the fluorine resin, there can also be used acrystalline polymer such as nylon, POM, PBT, PET, PPS, PEEK or the like;a polymer alloy; composite plastics consisting of plastics to whichreinforcing fibers or the like are added according to cases; and, thelike. Further, when there is used a sliding contact member 38 formed oflubricant containing resin which is a mixture of lubricating oil andsynthetic resin, the lubricant of the resin oozes out from the slidingcontact member 38 over a long period of time and is supplied to the ballscrew shaft 35, so that not only the critical speed of the ball screwshaft 35 can be enhanced but also the automatic lubrication of the ballscrew shaft 35 is possible.

[0049] The structure of the slider 33 may be similar to the ball screwnut employed in the conventional single shaft type table feed device.That is, as shown in FIG. 4, in the axially central portion of theslider main body 33 a, there is formed an insertion hole 39 throughwhich the ball screw shaft 35 can be inserted and, in the innerperipheral surface of the insertion hole 39, there is formed aspiral-shaped ball screw groove 39 a in such a manner as to correspondto the ball screw groove 35 a of the ball screw shaft 35. Also, thereare formed screw shaft insertion holes 40 respectively in the end caps33 b and 33 b which are fixed to the two end portions of the slider mainbody 33 a by bolts. In the upper portion of the slider main body 33 a,there is incorporated a U-shaped ball circulating tube 42 serving as aball-screw-system ball circulating passage which is used to guide andcirculate ball screw balls 41 respectively rolling within the ball screwgroove 35 a of the ball screw shaft 35 and the ball screw groove 39 aformed in the slider main body inside diameter surface and opposed tothe ball screw groove 35 a. The balls 41 are arranged in a known tubetype circulation structure in which the balls 41 are picked up from theball screw groove 35 a into the ball circulating tube 42, are movedalong the present tube 42 to climb over the land portion of the ballscrew shaft 35, and return again to the ball screw groove 35 a, so thatthey are circulated in an endless manner. By the way, the structure ofthe ball-screw-system ball circulating passage of the slider 33 servingas the movable body in the single shaft type table feed device accordingto the invention is not limited to the above-mentioned tube typecirculating structure but there can be used other types of known ballcirculating passage structures, for example, a circulating frame type ofball circulating passage structure, an end cap type of ball circulatingpassage structure, and the like.

[0050] Now, in the single shaft type table feed device structured in theabove-mentioned manner, a common table is previously mounted on theupper surfaces of the slider 33 and sub-slider 34. In this state, if theball screw shaft 35 is driven or rotated, then the slider 33 is allowedto act as a ball screw nut, that is, the slider 33 starts to move in theaxial direction thereof in compliance with the rotation of the ballscrew shaft 35. And, since the sub-slider 34 is connected with theslider 33 through the table, the sub-slider 34 moves similarly to theslider 33 in linking with the movement of the slider 33. The sub-slider34 moves while sharing the load applied to the table with the slider 33.At the same time, the sub-slider 34 is slidingly contacted with the ballscrew shaft 35 through the sliding contact member 38 mounted on theinside diameter surface of the sub-slider 34 to support the same,thereby performing the function of an intermediate support. That is, inthe conventional single shaft type table feed device, because anintermediate support cannot be installed between the slider 33 and thebearing for supporting the end portion of the ball screw shaft 35, thesupport distance of the ball screw shaft 35 becomes long and thus thecritical speed of the ball screw shaft 35 is restricted to a low speedlevel, which makes it difficult to increase the feeding speed of theslider 33. On the other hand, according to the present embodiment of theinvention, since the sub-slider 34 itself provides an intermediatesupport, the support distance of the ball screw shaft 35 can be reducedto thereby be able to enhance the critical speed of the ball screw shaft35. As a result, the high feeding speed of the single shaft type tablefeed device can be realized easily.

[0051] Embodiment 2

[0052] Now, description will be given below of a second embodiment of asingle shaft type table feed device according to the invention withreference to FIG. 5.

[0053] Here, FIG. 5 is a perspective view of a sub-slider 34 employed inthe second embodiment of a single shaft type table feed device accordingto the invention.

[0054] The present sub-slider 34 is different from that of thepreviously described first embodiment in that a fixing screw 45 is useda the fixing means for fixing the sliding contact member 38. Accordingto this fixing means, there is eliminated the need to restrict themovement of the sliding contact member 38 in the axial direction thereofby the end caps 34 b, and it is not necessary to match the whole lengthof the sliding contact member 38 to the length of the sub-slider mainbody 34 a. Therefore, according to the second embodiment, there can beprovided an advantage that a slidingly contact member 38 of a shorterlength can be used. The remaining operations and effects of the secondembodiment are similar to those of the first embodiment.

[0055] Embodiment 3

[0056] Now, FIG. 6 is a perspective view of a sub-slider 34 employed ina third embodiment of a single shaft type table feed device according tothe invention.

[0057] The present sub-slider 34 is different from those of thepreviously described first and second embodiments in that acylindrical-shaped sliding contact member 38 is divided in theperipheral direction thereof into a plurality of divisional sections,the divisional sections of the sliding contact member 38 are arranged insuch a manner as to surround the outer periphery of the ball screw shaft35, are fastened by an elastic body 46 such as a garter spring or thelike, and are mounted on the inside diameter surface of the screw shaftinsertion hole 37 of the sub-slider main body 34 a. The third embodimentis advantageous in that the mounting of the cylindrical-shaped slidingcontact member 38 can be achieved more easily than when it is insertedby pressure into the screw shaft insertion hole 37. Also, when thesliding contact member is formed of material containing a lubricanttherein, there can be provided an advantage that, due to the action ofthe elastic body, the inside diameter surface of the sliding contactmember is pressed against the outside diameter surface of the ball screwshaft to thereby be able to supply the lubricant to the ball screw shafteffectively. The remaining operations and effects of the thirdembodiment are similar to those of the first embodiment.

[0058] By the way, in the above-mentioned respective embodiments, therehas been illustrated an arrangement in which the sliding contact member38 is mounted on the inside diameter surface of the screw shaftinsertion hole 37 of the sub-slider main body 34 a. However, themounting portion of the sliding contact member 38 according to theinvention is not limited to this arrangement. For example, the slidingcontact member 38 may be mounted on the inside diameter surface(s) ofone or both of the end caps 34 b respectively mounted on the front andrear end portions of the sub-slider main body 34 a, provided that theresistance-to-load of the single shalt type table feed device is notdegraded.

[0059] In the above-mentioned respective embodiments, there has beenillustrated an example in which the inside diameter of the auxiliarymovable body is slidingly contacted with the outside diameter surface ofthe feed screw shaft. However, even if the auxiliary movable body is notslidingly contacted with the outside diameter surface of the feed screwshaft, the auxiliary movable body can be made to play the part of anintermediate support. That is, if a clearance between the insidediameter of the auxiliary movable body and the outside diameter surfaceof the feed screw shaft is set in such a manner as to have a size which,when the feed screw shaft is vibrated, allows the outside diametersurface of the feed screw shaft to be contacted with the inside diameterportion of the auxiliary movable body, then the resonance of the feedscrew shaft can be prevented, that is, the auxiliary movable body can bemade to play the part of an intermediate support.

[0060] As has been described heretofore, with use of a single shaft typetable feed device according to the invention, by arranging the auxiliarymovable body in such a manner as to be able to play the part of anintermediate support, the critical speed of the feed screw shaft can beenhanced and thus the increased feeding speed of the single shaft typetable feed device can be realized easily.

[0061] This application claims the benefit of Japanese Application No.Hei. 10-17454 which is hereby incorporated by reference.

[0062] While there has been-described in connection with the preferredembodiment of the invention, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the invention, and it is aimed, therefore, to cover inthe appended claim all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:
 1. A single shaft type table feed device comprising:a single feed screw shaft extending in an axial direction; a guide railextending in parallel with said screw shaft; a movable body movablysupported by said guide rail and fed by said screw shaft in the axialdirection; and an auxiliary movable body disposed apart from saidmovable body in the axial direction for supporting said table, saidauxiliary movable body being movably supported by said guide rail in theaxial direction and being moved in linking with a movement of a tablemounted on said movable body.
 2. The single shaft type table feed deviceaccording to claim 1 , wherein said auxiliary movable body includes aninside diameter portion through which said feed screw shaft can beinserted, and the inside diameter portion of said auxiliary movable bodyis contactable with the said feed screw shaft.
 3. The single shaft typetable feed device according to claim 2 , wherein the inside diameterportion of said auxiliary movable body is disengaged with said feedscrew shaft in a normal operation, but is contactable with the feedscrew shaft when said feed screw shaft is vibrated.
 4. The single shafttype table feed device according claim 2 , wherein the inside diameterportion of said auxiliary movable body is slidably contacted with thesaid feed screw shaft.
 5. The single shaft type table feed deviceaccording to claim 2 , wherein said auxiliary movable body comprises: asliding contact member brought in sliding contact with said feed screwshaft.
 6. The single shaft type table feed device according to claim 5 ,wherein said sliding contact member is divided into a plurality ofsegments.
 7. The single shaft type table feed device according to claim6 , wherein said sliding contact member are divided into a plurality ofsegments in a peripheral direction thereof, and said segments areassembled by an elastic body.
 8. The single shaft type table feed deviceaccording to claim 5 , wherein said auxiliary movable body furthercomprises: a main body portion movably supported by said guide rail,said main body portion being coupled with said sliding contact memberthrough a fastening member.
 9. The single shaft type table feed deviceaccording to claim 2 , wherein said auxiliary movable body comprises: asliding contact member brought in sliding contact with said feed screwshaft and is formed in a cylindrical shape.
 10. The single shaft typetable feed device according to claim 2 , wherein said sliding contactmember in the form of said cylindrical shape are divided into aplurality of segments.
 11. The single shaft type table feed deviceaccording to claim 10 , wherein said sliding contact member are dividedinto a plurality of segments in a peripheral direction thereof, and saidsegments are assembled by an elastic body.
 12. The single shaft typetable feed device according to claim 9 , wherein said auxiliary movablebody further comprises: a main body portion movably supported by saidguide rail, said main body portion being coupled with said slidingcontact member through a fastening member.
 13. The single shaft typetable feed device according to claim 5 , wherein said sliding contactmember comprises a lubricant containing member.
 14. The single shafttype table feed device according to claim 5 , wherein said auxiliarymovable body is brought in threadedly engagement with said feed screwshaft.